無線車載資通訊系統之車輛偵測及通道分析研究

Vehicle Detection and Channel Analysis of Wireless Telematics Systems

王柏仁(Pao-Jen Wang)

指導教授 ： 李學智

國立臺灣大學/電機資訊學院/電信工程學研究所/博士(2009年)

https://doi.org/10.6342/NTU.2009.00048

摘要

摘 要

為了達到高效率的交通運輸，智慧型運輸系統(ITS)整合了網路、資訊、電子及管理等技術，收集各種道路交通資訊，並且透過車輛與車輛，或車輛與道路旁的通訊設備將訊息傳送出去；當車道上有交通事故發生時，能透過車間通訊(IVC)通知後方車輛，使得道路駕駛能更為順暢並且更為安全。
車輛偵測器是為了快速提供道路車流資訊，能有效管理道路交通的設備，是ITS的重要工具之一；目前較為常用的道路車輛偵測器為迴圈式車輛偵測器及影像車輛偵測器。其中，傳統迴圈式車輛偵測器必須安置在車道上，安置的困難度較高，而且所獲得的車流資訊不多；而影像車輛偵測器則是設備成本較高、資料的分析較複雜，並且極易受環境影響，如夜間、雨天及灰塵等狀況都會使接收信號變差。本論文提出簡單且有效率的微波系統作為道路車輛偵測器，使用一組含發射及接收的天線，並且配合車輛通過感測區域時，通道感測信號特性的變化，可以同時對於多輛車經過多車道進行偵測，利用適當的演算法計算出各種有用的訊息，例如車輛位置、速度及類型(小車或大車)等。另外也提出使用陣列天線作為車輛偵測器的接收端，利用陣列天線對車輛反射信號的角度偵測，也可以同時判斷出多輛車的位置及速度。
對於IVC的訊息傳送，有效的信號傳送距離與車道上車輛裝設通訊設備的比率以及IVC的無線通道特性的好壞有關。在IVC中，若信號發送車輛與信號接收車輛之間存在沒有裝設通訊設備的車輛時，則此沒有裝設通訊設備的車輛對於IVC的信號傳送可以被當成是遮蔽物，因此信號是以非直接波傳送；當信號發送車輛與信號接收車輛之間沒有存在車輛遮蔽時，則此時IVC的信號傳送之間沒有遮蔽物，因此信號是以直接波傳送。本論文對於IVC存在遮蔽車輛的情形做實際量測，並且提出適當的繞射模型及遮蔽車輛的三路模型做模擬，觀察因為遮蔽所產生的電波衰減，並且計算考慮衰減的情況下，IVC信號的有效傳送距離的變化。最後，我們也使用實際測量及模擬驗證，提出在接收端使用多天線的空間分集方法，達到提高IVC在有遮蔽情況下的有效傳送距離。

關鍵字

智慧型運輸系統 ； 車輛偵測器 ； 陣列天線 ； 車間通訊 ； 遮蔽效應 ； 空間分集

並列摘要

Abstract

In order to achieve efficient traffic control, Intelligent Transportation System (ITS) has been widely deployed in many regions such as America, Europe, Australia, Japan, and Taiwan. ITS integrates various methods to extract useful information such as the vehicle location, speed, type (a small car or a big car) etc. In addition, to manage the serious traffic problems and prevent the unnecessary personal injuries, ITS adopts the inter-vehicle communications (IVC) to inform the drivers if there are accidents nearby.
In this dissertation, we propose a channel awareness vehicle detection which employs only one single transmitter-receiver antenna pair to perform the multi-lane and multi-vehicle identifications simultaneously. By using the characteristics of channel variations, the proposed vehicle detection can determine the vehicle location, speed, and type. Our field-measurement results demonstrated its capabilities. Besides, we also propose a vehicle detection system of microwave that can extract multi-lane traffic information via using an antenna array. The proposed system adopts the multiple signal classification (MUSIC) algorithm to identify the vehicle location and speed.
Regarding to transmit the information in the IVC, the ability of effective transmission distance of the emergency information depends notably on the percentage of the vehicles equipped with communication device and the characteristics of radio wave propagation. The vehicles which are not equipped with these communication devices will block the radio propagation and result in the undesirable shadowing attenuation. Hence, we survey the impact of the shadowing effect for the IVC via the computer simulations and the field-measurements. Besides, a modified three-ray shadowing model suitable for the IVC is proposed. Finally, we use the field-measurements to evaluate the spatial diversity performance of the IVC system under different wireless channels. Combined with the three-ray shadowing model, the range extension capability by using the two receiving antennas is evaluated.

並列關鍵字

ITS (Intelligent Transportation System) ； Vehicle detector ； Antenna array ； IVC (Inter-Vehicle Communication) ； Shadowing effect ； Spatial diversity

參考文獻

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